Manufacturers have been successfully applying Parker Sporlan Thermostatic Expansion Valves on Heat Pump Applications for many years. Parker Sporlan's large diaphragm and durable welded element result in unmatched thermostatic expansion valve quality and life. In this blog we discuss using thermostatic expansion valves on different types of heat pump systems.
Many variations and matches of expansion devices have been used to regulate flow to the evaporator coils of a heat pump system. Optimum control is achieved by employing two thermostatic expansion valves, one to feed each coil as shown in Figure 1. Each valve can be tuned to control desired superheat for uniquely different coils and operating conditions.
The durable construction of the standard Parker Sporlan valve is ideal for heat pump applications. It is recommended that the external equalizer be connected to the common suction line, as shown in Figure 1. The underside of the diaphragm will be exposed to high side pressures if the equalizer is connected to the suction line ahead of the reversing valve. Parker Sporlan diaphragms can withstand these pressures but discharge pulsations are a possible source of problems. Discharge pulses can be dampened but the OEM tests should be performed to prove reliability. When using a thermostatic expansion valve to control flow in one direction only, as shown in Figure 1, there are two options available:
The "Bi-Directional" Thermostatic Expansion Valve has successfully been used to replace two expansion devices as shown in Figure 2. It controls refrigerant flow to either coil when the coil is serving as the system evaporator. The Bi-Directional valve is generally applied on packaged units with close coupled components. The bulb and external equalizer are mounted to the common suction line. The suggested flow direction for the Bi-Directional valve is with the valve flowing in its normal direction when the system is in the heating mode. This flow direction will normally result in a lower superheat in the heating mode. The preferred flow direction for each application should be verified by testing. There are two valves which have been designed for Bi-Directional applications. The ER valve which is available to wholesale customers and the BBI valve which is only available to OEM customers. These valves are available in capacities through a nominal 15 tons, R-410A.
For more information on applying filter-driers in the same heat pump system please see Bulletin 240-10-2.
HVACR Tech Tip Article contributed by Jason Forshee, application engineer, Sporlan Division of Parker Hannifin
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